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><H1
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><A
NAME="TUNER"
>1.6. Tuners and Modulators</A
></H1
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN396"
>1.6.1. Tuners</A
></H2
><P
>Video input devices can have one or more tuners
demodulating a RF signal. Each tuner is associated with one or more
video inputs, depending on the number of RF connectors on the tuner.
The <CODE
CLASS="STRUCTFIELD"
>type</CODE
> field of the respective
struct&nbsp;<A
HREF="r8936.htm#V4L2-INPUT"
>v4l2_input</A
> returned by the <A
HREF="r8936.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_ENUMINPUT</CODE
></A
> ioctl is set to
<CODE
CLASS="CONSTANT"
>V4L2_INPUT_TYPE_TUNER</CODE
> and its
<CODE
CLASS="STRUCTFIELD"
>tuner</CODE
> field contains the index number of
the tuner.</P
><P
>Radio devices have exactly one tuner with index zero, no
video inputs.</P
><P
>To query and change tuner properties applications use the
<A
HREF="r12342.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_G_TUNER</CODE
></A
> and <A
HREF="r12342.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_S_TUNER</CODE
></A
> ioctl, respectively. The
struct&nbsp;<A
HREF="r12342.htm#V4L2-TUNER"
>v4l2_tuner</A
> returned by <CODE
CLASS="CONSTANT"
>VIDIOC_G_TUNER</CODE
> also
contains signal status information applicable when the tuner of the
current video input, or a radio tuner is queried. Note that
<CODE
CLASS="CONSTANT"
>VIDIOC_S_TUNER</CODE
> does not switch the current tuner,
when there is more than one at all. The tuner is solely determined by
the current video input. Drivers must support both ioctls and set the
<CODE
CLASS="CONSTANT"
>V4L2_CAP_TUNER</CODE
> flag in the struct&nbsp;<A
HREF="r13105.htm#V4L2-CAPABILITY"
>v4l2_capability</A
>
returned by the <A
HREF="r13105.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_QUERYCAP</CODE
></A
> ioctl when the device has one or
more tuners.</P
></DIV
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN418"
>1.6.2. Modulators</A
></H2
><P
>Video output devices can have one or more modulators, uh,
modulating a video signal for radiation or connection to the antenna
input of a TV set or video recorder. Each modulator is associated with
one or more video outputs, depending on the number of RF connectors on
the modulator. The <CODE
CLASS="STRUCTFIELD"
>type</CODE
> field of the
respective struct&nbsp;<A
HREF="r9149.htm#V4L2-OUTPUT"
>v4l2_output</A
> returned by the <A
HREF="r9149.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_ENUMOUTPUT</CODE
></A
> ioctl is
set to <CODE
CLASS="CONSTANT"
>V4L2_OUTPUT_TYPE_MODULATOR</CODE
> and its
<CODE
CLASS="STRUCTFIELD"
>modulator</CODE
> field contains the index number
of the modulator. This specification does not define radio output
devices.</P
><P
>To query and change modulator properties applications use
the <A
HREF="r11430.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_G_MODULATOR</CODE
></A
> and <A
HREF="r11430.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_S_MODULATOR</CODE
></A
> ioctl. Note that
<CODE
CLASS="CONSTANT"
>VIDIOC_S_MODULATOR</CODE
> does not switch the current
modulator, when there is more than one at all. The modulator is solely
determined by the current video output. Drivers must support both
ioctls and set the <CODE
CLASS="CONSTANT"
>V4L2_CAP_TUNER</CODE
> (sic) flag in
the struct&nbsp;<A
HREF="r13105.htm#V4L2-CAPABILITY"
>v4l2_capability</A
> returned by the <A
HREF="r13105.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_QUERYCAP</CODE
></A
> ioctl when the
device has one or more modulators.</P
></DIV
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN437"
>1.6.3. Radio Frequency</A
></H2
><P
>To get and set the tuner or modulator radio frequency
applications use the <A
HREF="r11094.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_G_FREQUENCY</CODE
></A
> and <A
HREF="r11094.htm"
><CODE
CLASS="CONSTANT"
>VIDIOC_S_FREQUENCY</CODE
></A
>
ioctl which both take a pointer to a struct&nbsp;<A
HREF="r11094.htm#V4L2-FREQUENCY"
>v4l2_frequency</A
>. These ioctls
are used for TV and radio devices alike. Drivers must support both
ioctls when the tuner or modulator ioctls are supported, or
when the device is a radio device.</P
></DIV
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN445"
>1.6.4. Satellite Receivers</A
></H2
><P
>To be discussed. See also
proposals by Peter Schlaf, video4linux-list@redhat.com on 23 Oct 2002,
subject: "Re: [V4L] Re: v4l2 api".</P
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